Polyethylene terephthalate (hereinafter sometimes referred to as “PET”) is a polyester resin that is characterized by excellent transparency, mechanical strength, melt stability, solvent resistance, aroma retaining properties, and recyclability, and is widely utilized in film, sheet, hollow containers, and the like. However, it cannot be said that PET has a sufficiently high glass transition temperature, also transparency may be impaired due to its crystallinity when a thick molded, article is obtained, and therefore modification by copolymerization is widely carried out.
For example, polyester resins are proposed in which 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, or pentacyclopentadecanedimethanol is used as a copolymerization component for polyesters. Since tricyclodecanedimethanol and pentacyclopentadecanedimethanol have a bulky, rigid skeleton, polyester resins involving these have a high glass transition temperature, the crystallinity is suppressed, and it is thus possible to increase the transparency of a molded article (see, for example, Patent Literatures 1 and 2).
On the other hand, among the aliphatic polyesters in which completely no aromatic components are used, polyesters with an alicyclic structure have excellent transparency and water resistance, and thus a large number of methods involving an alicyclic monomer represented by 1,4-cyclohexanedimethanol are proposed. For example, Patent Literature 3 discloses an aliphatic polyester composed of 1,4-cyclohexanedimethanol with 1,4-cyclohexanedicarboxylic acid or the like. Also, for increased heat resistance of aliphatic polyesters, polyesters having a norbornane skeleton are proposed (see, for example, Patent Literatures 4 and 5).